Electric fuse.



C. W. DAVIS.

ELECTRIC FUSE.

APPLICATION FILED JULY 22. 1913.

1,152,149. Patented Aug. 31,1915.

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WITNESSESW C. W. DAVIS.

ELECTRIC FUSE.

APPLICATION FILED JULY 22. 1913.

1,152,149. Patented Aug. 31, 1915.

2 SHEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

CHARLES W. DAVIS, OF EDGEWORTH, PENNSYLVANIA, ASSIGNOR TO STANDARD UNDERGROUND CABLE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A COR- PORATION OF PENNSYLVANIA.

ELECTRIC FUSE.

Specification of Letters Patent.

Patented Aug. 31, 1915.

Application filed July 22, 1913. Serial No. 780,545.

To all whom it may concern Be it known that I, CHARLES W. DAVIS, residing at Edgeworth, in the county of Allegheny and State of Pennsylvania, a citizen of the United States, have invented or discovered certain new and useful Improvements in Electric Fuses, of which improvements the following is a specification.

My invention relates to fuse structures adapted to interrupt electrical circuits when the current carried thereby becomes abnormal or dangerous.

One object of my invention is to provide an improved form of junction-box for oil fuses, whereby the fusible element may be easily renewed and the structure placed in circuit within such box without endangering the workman, and which box will also serve as an effective circuit breaker when the circuit is carrying a normal current.

A further object of my invention is to provide a fuse structure which will, with minimum explosive results, effectively break a circuit when overloaded or when shortcircuited.

My invention is illustrated in the accompanying drawings which form part of my specification, and in which Figure 1 is a vertical sectional view of a fuse junction box, part of the fuse casing being shown in central longitudinal section,

the plane of section of the junction box being indicated by the line I I, Fig. 2; Fig. 2 is an end view of the box, partly in section, the plane of view being indicated by the line II-II, Fig. 1; and Fig. 3 is a view in elevation of an alternate form of fuse oasing. Fig. l is a fragmentary view corresponding to Fig. 1 and illustrating an alternate detail of structure.

In the several figures like numerals are used to designate like parts. I

Having reference first to the construction of the junction box illustrated herein, and

subsequently to the fuse structure, the box,

which is preferably made of cast iron, is formed of two parts, a bottom portion 1 and a lid 2, pivoted to one side of the bottom portion, as at 3. The bottom wall of the boxis provided with suitable cable terminals 4, which have spring clips 5 at their upper ends, adapted to be electrically connected to cable conductors, and to receive the knife-blade contacts 6 of the fuse casing 7. The fuse casing 7, which may be of any deslred interior construction, is pro vided at its opposite ends with brackets in the form of collars 8, to which the knifeblade contacts 6 are secured, and which in turn are secured at their upper ends to a suitable frame or carrier 9. When installed and in operation, boxes of this general character are filled with an arc-dampening liquid, such as oil or carbon tetra-chlorid, to the approximate level indicated in the drawings, thus rendering the spring clips or other electrical contacts invisible. In case a fuse blows, it becomes necessary, of course, to remove the casing, renew the fuse strip and return the casing to its proper position. However, there is a possibillty, when the fuse casing is being replaced, that a. short circuit still transgresses the line, in which event a relatively violent explosion is liable to occur when contact is made between contacting members of box and fuse structure, such explosion being of sufiicient strength to throw a volume of liquid from the box and upon the workman replacing the fuse structure. In order to properly guide the fuse casing to its desired position within the box, I preferably pivot the frame 9 by means of a rigid arm 10 to the box portion 1, the box being suitably offset at 11 for this purpose, as is clearly shown. Also, in order to prevent the liquid from being thrown from the casing when the fuse structure is being replaced, I provide a track, preferably in the form of a slot 11, on the under side of the lid 2, and, by means of a hanger 12, suspend the frame 9 from such track, the lid 2 being provided with downwardly-extending walls adapted to telescope with a shield 13 secured to the walls of the box. The arrangement of the box and fuse structure in this regard is such that, when the lid is being lowered to place the fuse structure in operative position, electrical contact will not be completed between the contact clips 5 and the knifeblades 6 until the outer end of the lid has passed below the upper edge of the shield 13.

To the end that the lid 2 may be held yieldingly in closed position, clamping bolts 1 1, provided with thumb screws 15 and with compression springs 16, are pivoted to the box walls, and lugs 17, having open-ended slots, are secured to the lid 2, said springs bearing at opposite ends upon the thumbscrews 15 and lugs 17.

Another feature of my invention concerns the construction of the fuse structure proper. l have founc that the explosive results of oil fuses may be very materially diminished by first providing a fuse casing which will afford an air-pocket adjacent to the fusible element of the conductor, and secondly providing rigid leads or terminals for the fusible element, such leads extend; ing through small. apertures beneath a body of arc dampening liquid, the arrangement being such that, when the fusible element blows, the explosive forces generated thereby will compress the air in the air pocket or chamber, such compressed air and vapor subsequently escaping rapidly preferably through the lead apertures and preferably in line with the leads, which are not moved by the explosive forces. in the drawings 1 have illustrated two fuse casings embodying this feature of my invention. The casing of Figs. 1 and 2 consists of a horizontally disposed cylindrical portion 7, through the center of which a smaller cylinder 18 extends vertically. .he rigid leads 19,

which are suitably secured at their outer ends to the knife-blade contacts (3, extend through the casing 7 and into the cylinder 18, the apertures 20 through which the leads extend being slightly larger than the di ameter of the leads. The fusible element 21 connecting the inner ends of the leads may lie entirely beneath the liquid as shown in Fig. 1, or it may be bowed upwardly above the surface of the liquid, shown in Fig. 1. The leads 19 may be of any desired conductive material of such rigidity that the leads will remain unmoved, or but slightly moved, by the explosive forces. is an example of the leads that may be used, I have obtained very good results with heavy copper wire and with copper covered steel wire. In order to batlle the expansive action of the forces of explosion, as well as to consume a portion'of the released energy, I mount a series of transversely extending plates in the casing portion 7. These baffles preferably comprise a plurality of relatively thin semi-circular plates 22 extending from the upper portion of the casing 7, and forming between them alternate layers of air and liquid, and three heavier plates 23, spaced at greater intervals, one of the plates 23 extending from the bottom of the casing and the other two from the top at each side of the bottom plate. As will be clearly seen, an air pocket is formed between the top plates 23.

In operation, when the fusible element 21 blows, the vapor and gases are highly compressed in the air chamber above the normal position of the fusible element. These vapors immediately expand through the apertures 20 around the leads 19, and thus quickly disrupt the arc, the battle plates 22 and 23 being effective to destroy, to a very large extent, the force of the gases and vapors issuing through the aperture 20.

The form of fuse casing illustrated in Fig. 3 is of simpler construction than the one just described, and consists of a. single cylindrical casing 18 provided with apertures 20. In order to hold the rigid leads 19 in position both during the normal operation of the fuse and when it blows, arms are secured to the wall of the casing, as shown. If desired, the leads 19 may fit neatly in the apertures 20 and other openings made in the casing l8 below the aperture 20, and a system of bailie plates, similar to those illustrated in Fig. 1, may be placed in front of such holes. lhe operation of this form of fuse str cture is, except for he action of the bailie plates, the same as that of Figs. 1 and 2, and need not be again described.

l claim as my invention:

1. In a junction box for oil, fuses, the combination with a casing provided with conductor terminal. and contact elements and further provided with a body of arc-dampening liquid, a lid to said casing, an electric fuse structure movable with said lid and partially engaging said contacts before said lid is completely closed; and means, effective while said fuse structure being placed in contact with said elements, for preventing the expulsion of the arc-dampening liquid from the casing and between the partly closed lid and the edges of the casing adjacent thereto.

In a junction-box for oil fuses, the combination with a casing provided with conductor terminals and clips and adapted to hold a body of arc-dampening liquid, a lid pivoted to said casing and having a peripheral flange, an electric fuse structure movable with said lid, and a bail'le plate extending upwardly from the seated position of said lid and adapted to telescope within the flange thereof.

In a junction-box for oil fuses, the combination with a casing provided with conductor terminals and clips, and further provided with a body of arc-dampening liquid, a lid pivoted to said casing, and an electric fuse structure pivoted to said casing and having movable engagement with said lid, said fuse structure being movable with said lid to and from engagement with the terminal clips.

1-. In an electric fuse, the combination of a receptacle containing a body of arc-dampening liquid, a fuse casing therein indestructible by the blowing of a fuse and provided with a lead-entering aperture in its wall below the surface of said liquid, said aperture permitting the arc-dampening ening liquid, a fuse casing therein indestructible by the blowing of a fuse and provided with oppositely-disposed lead-entering apertures in its wall below the surface of said liquid, said apertures permitting the arc-dampening liquid to enter the casing, rigid leads extending through said apertures and having their ends within the casing connected to a fusible element, and an auxiliary chamber formed by the walls of said casing and wherein pneumatic pressure is stored on the blowing of the fusible element and from which such pressure is in turn exerted to produce an arc-preventing flow of said liquid.

6. In an electric fuse, the combination of a receptacle containing a body of arc-dampening liquid, a fuse casing therein indestructible by the blowing of a fuse and provided with a lead-entering aperture in its wall below the surface of said liquid, said aperture permitting the arc-dampening liquid to enter the casing, a rigid lead ex tending through said aperture and con nected within said casing to a fusible element, an auxiliary chamber wherein pneumatic pressure is stored on the blowing of the fusible element and from which such pressure is in turn exerted to produce an arc-preventing flow of said liquid, and bafiie plates adjacent to said casing aperture.

7 In an electric fuse, the combination of a receptacle containing a body of arc-dampening liquid, a fuse casing therein and provided wit-h a lead-entering aperture in its wall, said aperture permitting the arc-dampening liquid to enter the casing, a lead conductor extending through and incompletely filling said aperture and consisting of a body of rigid material provided with a coating of low resistance material, a fusible element within the casing in electrical connection with said lead, and an auxiliary chamber wherein pneumatic pressure is stored on the blowing of the fusible element and from which such pressure is in turn exerted to produce an arc-preventing flow of said liquid.

8. In an electric fuse, the combination of a receptacle containing a body of arc-dampening liquid, a fuse casing therein indestruotible by the blowing of a fuse and provided with a lead-entering aperture in its wall, said aperture permitting the arc-dampening liquid to enter the casing, a rigid lead conductor consisting of a copper coated steel wire extending through and incompletely filling said aperture, a fusible element within the casing and in electrical connection with said lead, and an auxiliary chamber wherein pneumatic pressure is stored on the blowing of the fusible element and from which such pressure is in turn exerted to produce an arc-preventing flow of said liquid.

In testimony whereof I have hereunto set my hand.

CHARLES W. DAVIS.

Witnesses VINTON SMITH, J. LAWRENCE LYON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

